In military operations it is sometimes necessary to render an area impassable by use of land mines which explode to destroy vehicles attempting to pass. A system is known by which mines are dispensed automatically from a supply carried by a vehicle, the mines being projected to fall on the ground at a distance from the vehicle, and having pre-arming, arming, and self-destruct circuitry. The mines are of short, circularly cylindrical configuration, and for proper operation must be dispensed with a spin about the axis of the cylinder. They are referred to as GEMSS mines and the dispenser is given the identification XM128: details of this equipment are not necessary to an understanding of the present invention, which comprises a back-up for the XM128 to enable dispensing of the mines to continue, if somewhat less rapidly, should the XM128 become disabled.